This invention relates to improvements in easy opening closures, and more particularly to improvements in pressure releasing vent closures of the type presently used in can ends having push-in closures.
It is generally accepted in the can making art that a can having push-in closures requires, for highly carbonated beverages, some form of pressure releasing venting closure by means of which the pressure within the can may be at least reduced prior to opening the pouring closure. An example of a pressure releasing venting closure is shown in FIG. 1 of the accompanying drawings, in which it will be noted that the venting closure V is smaller in area than the pouring closure P.
Cans containing highly carbonated beverages, including those having venting closures as shown in FIG. 1, are liable to gush or spurt on being opened, especially where the beverage in the can tends to froth. The problem is aggravated when the can is tilted during the opening operation since this often means that the liquid in the can is close to or covers the venting closure whereby the escaping gas is more likely to entrain some of the liquid or froth in the can. The problem is even more aggravated where the can is roughly handled prior to the opening thereof since agitation causes the release of carbon dioxide into the can head space, thereby generating froth.
U.S. Pat. No. 2,261,117 to Jack, Jr., discloses a push-in closure comprising a single closure member. The closure member is formed by forming a bulge in the container member, severing around the bulge to form a severed bulged tab, and then flattening the bulged tab to place the cut edges thereof and the marginal portions surrounding the opening in overlapping relationship.
U.S. Pat. No. 3,334,775 to Klein et al discloses a gated can lid wherein the gate is depressible into the container by digitally applied push-in force. The container has a single gate therein, but the patentees describe, at column 4, lines 62 - 66, an arrangement wherein a portion of the gate panel might be folded inwardly from each end to provide a specific pouring portion and a venting portion, with the section of the gate panel between these portions remaining in position. Klein et al do not disclose or suggest a resealable venting member.
U.S. Pat. 3,741,432 to Werth et al and Australian Pat. No. 475,951 each disclose a closure tab for a container, with a pressure release tab formed in the closure tab. Manual pressure applied to the pressure release vent tab is transferred to the closure tab. Both the release vent tab and the closure tab are depressible by the pressure of the user's thumb applied to the release vent closure tab and transmitted to the closure tab in a single operation which first exposes the release vent and then the closure vent or opening. Werth et al have no suggestion that the pressure release vent tab disclosed therein is resealable upon the release of digitally applied push-in force. As a matter of fact, the entire thrust of the Werth et al patent is to permit the pressure to be vented and the pouring opening to be opened in one operation without withdrawing a digit from the tab area.
U.S. Pat. Nos. 3,759,206 (Re. 28,910) and 3,931,909 are directed to push-in, easy opening closures for containers such as metal beverage cans. The patents disclose forming the easy opening closures by bulging an area of a can end, or other container member, and cutting a tab from the container member, with at least a portion of the bulge lying outside of and surrounding the tab. After the severing or cutting operation, the bulge surrounding the opening is flattened to displace the metal into overlapping relationship with the cut edges of the tab.
U.S. Pat. No. 3,958,717 to Ellis discloses a push-in, easy opening closure which includes a pouring tab and a vent tab. The tabs are integrally connected to the can lid by a hinge area, and share a common hinge area, with the tabs extending in opposite direction from the common hinge area. The patentees indicate that this construction results in an appearance similar to a conventional ring-pull end, so special instructions would not be required to educate the consumer, and also with the tabs located immediately adjacent to each other the can can be opened with a minimum of finger movement. There is no suggestion that the vent tab reseals itself upon the removal of finger pressure applied thereto.
U.S. Pat. No. 4,033,275 to Radtke discloses a beverage can end having a vent tab and a pour tab, generally similar to the design of U.S. Pat. No. 3,958,717, except the tabs do not share a common hinge area, but instead are disclosed as remote from one another.
It is thus an object of the present invention to provide improved forms of pressure releasing closure by means of which the gushing or spurting problem described above is at least alleviated or made more controllable.